When jetting off on holiday, we rarely give a second thought to what microbes we might be taking with us. But humans spread trillions of bacteria around the globe, potentially harming ecosystems' balance.

Three stories about researchers who have dabbled in self-experimentation – with varying results.
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New research suggests our gut microbes have their own circadian rhythms that in turn influence our organ functions. Is this an explanation for how disrupting our daily patterns can cause health problems?